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  <head>
    <meta charset="UTF-8" />
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    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
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  <body>
    <!-- 写出⼀个1到10 的数组，少写⼀个数字，利⽤函数将少写的数字找出来。少写 9 把 9 找出来 -->
    <script>
      let arr = [1, 2, 3, 4, 5, 6, 7, 8, 10]
      let sum = 0
      for (let i = 0; i < arr.length; i++) {
        sum += arr[i]
      }
      console.log(55 - sum)
    </script>
  </body>
</html>
